Tesla CEO Elon Musk shows off the Tesla Semi as he unveils the company's new electric semi truck during a presentation in Hawthorne, California, U.S., November 16, 2017.

Tesla announced plans to make an electric semi in November last year, garnering buzz and pre-orders from major customers including Pepsi, Walmart and Anheuser-Busch. Now, the company is testing its prototype semis on the open road in California and Nevada.

Tesla CEO Elon Musk shared photos of a cargo-hauling test drive with his legions of followers on Instagram and Twitter on Wednesday.

The truck in the photos featured side-view mirrors. When Tesla originally showed off its Semi prototypes last year, they did not feature analog mirrors. Instead the company said they would use cameras to give drivers a comprehensive view of their surroundings.

That doesn't mean the Tesla Semi will have traditional side-view mirrors, however. When auto makers test prototypes, their vehicles can include parts in various stages of readiness. The Tesla Semis that have been spotted in the wild, and shown off today by Musk, aren't precisely representative of the final production vehicles.

While Tesla has told investors it would start mass-production of its electric semis in 2019, the company has yet to announce where these trucks will be manufactured.